As a conventional technique, a foam dispenser is known that includes a placing tubular portion adapted to be fitted to a neck of a container body, and a standing tubular portion standing from an inner circumference of a flange-shaped top wall portion of the placing tubular portion. In this instance, an air cylinder is suspended from the flange-shaped top wall portion, and a tubular air piston is fitted in the air cylinder. The air piston has a partition wall provided with an ambient air introducing hole, and the partition wall of the air piston is slidably inserted in the air cylinder. A nozzle head is also placed over a stem standing from a liquid cylinder. (Refer to JP2007-253113A, for example.)